Marsh sediments chronically exposed to nitrogen enrichment contain degraded organic matter that is less vulnerable to decomposition via nitrate reduction.

Blue carbon habitats, including salt marshes, can sequester carbon at rates that are an order of magnitude greater than terrestrial forests. This ecosystem service may be under threat from nitrate (NO3-) enrichment, which can shift the microbial community and stimulate decomposition of organic matter. Despite efforts to mitigate nitrogen loading, salt marshes continue to experience chronic NO3- enrichment, however, the long-term consequence of this enrichment on carbon storage remains unclear. To investigate the effect of chronic NO3- exposure on salt marsh organic matter decomposition, we collected sediments from three sites across a range of prior NO3- exposure: a relatively pristine marsh, a marsh enriched to ~70 µmol L-1 NO3- in the flooding seawater for 13 years, and a marsh enriched between 100 and 1000 µmol L-1 for 40 years from wastewater treatment effluent. We collected sediments from 20 to 25 cm depth and determined that sediments from the most chronically enriched site had less bioavailable organic matter and a distinct assemblage of active microbial taxa compared to the other two sites. We also performed a controlled anaerobic decomposition experiment to test whether the legacy of NO3- exposure influenced the functional response to additional NO3-. We found significant changes to microbial community composition resulting from experimental NO3- addition. Experimental NO3- addition also increased microbial respiration in sediments collected from all sites. However, sediments from the most chronically enriched site exhibited the smallest increase, the lowest rates of total NO3- reduction by dissimilatory nitrate reduction to ammonium (DNRA), and the highest DNF:DNRA ratios. Our results suggest that chronic exposure to elevated NO3- may lead to residual pools of organic matter that are less biologically available for decomposition. Thus, it is important to consider the legacy of nutrient exposure when examining the carbon cycle of salt marsh sediments.

The Microbial Ecology of Estuarine Ecosystems.

Human civilization relies on estuaries, and many estuarine ecosystem services are provided by microbial communities. These services include high rates of primary production that nourish harvests of commercially valuable species through fisheries and aquaculture, the transformation of terrestrial and anthropogenic materials to help ensure the water quality necessary to support recreation and tourism, and mutualisms that maintain blue carbon accumulation and storage. Research on the ecology that underlies microbial ecosystem services in estuaries has expanded greatly across a range of estuarine environments, including water, sediment, biofilms, biological reefs, and stands of seagrasses, marshes, and mangroves. Moreover, the application of new molecular tools has improved our understanding of the diversity and genomic functions of estuarine microbes. This review synthesizes recent research on microbial habitats in estuaries and the contributions of microbes to estuarine food webs, elemental cycling, and interactions with plants and animals, and highlights novel insights provided by recent advances in genomics.

Diversity at single nucleotide to pangenome scales among sulfur cycling bacteria in salt marshes.

IMPORTANCE: Salt marshes are known for their significant carbon storage capacity, and sulfur cycling is closely linked with the ecosystem-scale carbon cycling in these ecosystems. Sulfate reducers are key for the decomposition of organic matter, and sulfur oxidizers remove toxic sulfide, supporting the productivity of marsh plants. To date, the complexity of coastal environments, heterogeneity of the rhizosphere, high microbial diversity, and uncultured majority hindered our understanding of the genomic diversity of sulfur-cycling microbes in salt marshes. Here, we use comparative genomics to overcome these challenges and provide an in-depth characterization of sulfur-cycling microbial diversity in salt marshes. We characterize communities across distinct sites and plant species and uncover extensive genomic diversity at the taxon level and specific genomic features present in MAGs affiliated with uncultivated sulfur-cycling lineages. Our work provides insights into the partnerships in salt marshes and a roadmap for multiscale analyses of diversity in complex biological systems.

Salt marsh nitrogen cycling: where land meets sea.

Salt marshes sit at the terrestrial-aquatic interface of oceans around the world. Unique features of salt marshes that differentiate them from their upland or offshore counterparts include high rates of primary production from vascular plants and saturated saline soils that lead to sharp redox gradients and a diversity of electron acceptors and donors. Moreover, the dynamic nature of root oxygen loss and tidal forcing leads to unique biogeochemical conditions that promote nitrogen cycling. Here, we highlight recent advances in our understanding of key nitrogen cycling processes in salt marshes and discuss areas where additional research is needed to better predict how salt marsh N cycling will respond to future environmental change.

Microbial chemolithoautotrophs are abundant in salt marsh sediment following long-term experimental nitrate enrichment.

Long-term anthropogenic nitrate (NO3-) enrichment is a serious threat to many coastal systems. Nitrate reduction coupled with the oxidation of reduced forms of sulfur is conducted by chemolithoautotrophic microbial populations in a process that decreases nitrogen (N) pollution. However, little is known about the diversity and distribution of microbes capable of carbon fixation within salt marsh sediment and how they respond to long-term NO3- loading. We used genome-resolved metagenomics to characterize the distribution, phylogenetic relationships, and adaptations important to microbial communities within NO3--enriched sediment. We found NO3- reducing sulfur oxidizers became dominant members of the microbial community throughout the top 25 cm of the sediment following long-term NO3- enrichment. We also found that most of the chemolithoautotrophic genomes recovered contained striking metabolic versatility, including the potential for complete denitrification and evidence of mixotrophy. Phylogenetic reconstruction indicated that similar carbon fixation strategies and metabolic versatility can be found in several phylogenetic groups, but the genomes recovered here represent novel organisms. Our results suggest that the role of chemolithoautotrophy within NO3--enriched salt marsh sediments may be quantitatively more important for retaining carbon and filtering NO3- than previously indicated and further inquiry is needed to explicitly measure their contribution to carbon turnover and removal of N pollution.

Trends in early gestation stillbirths and neonatal deaths in New South Wales, Australia 2002-2019.

BACKGROUND: Little research has focused on understanding trends in early gestation (20-27 weeks) stillbirths and neonatal deaths. AIMS: To examine trends in early gestation stillbirths and neonatal deaths in New South Wales (NSW), Australia. MATERIALS AND METHODS: Population-based cohort study of all births ≥20 weeks gestation among female NSW residents during 2002 to 2019, induced pregnancy terminations excluded. Stillbirth rates by gestational age and birth year were calculated per 1000 fetuses-at-risk (FAR). Neonatal death rates by gestational age and birth year were calculated per 1000 live births. Linear regression was used to examine trends in stillbirth and neonatal death rates among all, singleton and twin births. RESULTS: Declining trends in early gestation stillbirth and neonatal death rates were found. Stillbirth rates decreased from 1.9 and 0.9/1000 FAR in 2002 to 1.6 and 0.7 in 2019 for 20-23 and 24-27 week groups, respectively. Neonatal rates decreased from 940 and 315/1000 live births in 2002 to 925 and 189 in 2019 for the 20-23 and 24-27 week groups, respectively. Among singleton births, declining trends in stillbirth and neonatal death rates across all age groups were observed, except for 37-38 week stillbirths. No trends in twin stillbirth rates were found across gestational age groups, although a decreasing trend was observed for 20-23 week twin neonatal deaths. CONCLUSIONS: Trends in early gestation stillbirth and neonatal deaths have declined in recent decades in NSW but further efforts are needed to reduce both early and late gestation stillbirth rates among twin births.

Pathways for Understanding Blue Carbon Microbiomes with Amplicon Sequencing.

The capacity of Blue Carbon Ecosystems to act as carbon sinks is strongly influenced by the metabolism of soil-associated microbes, which ultimately determine how much carbon is accumulated or returned to the atmosphere. The rapid evolution of sequencing technologies has facilitated the generation of tremendous amounts of data on what taxa comprise belowground microbial assemblages, largely available as isolated datasets, offering an opportunity for synthesis research that informs progress on understanding Blue Carbon microbiomes. We identified questions that can be addressed with a synthesis approach, including the high variability across datasets, space, and time due to differing sampling techniques, ecosystem or vegetation specificity, and the relationship between microbiome community and edaphic properties, particularly soil carbon. To address these questions, we collated 34 16S rRNA amplicon sequencing datasets, including bulk soil or rhizosphere from seagrass, mangroves, and saltmarshes within publicly available repositories. We identified technical and theoretical challenges that precluded a synthesis of multiple studies with currently available data, and opportunities for addressing the knowledge gaps within Blue Carbon microbial ecology going forward. Here, we provide a standardisation toolbox that supports enacting tasks for the acquisition, management, and integration of Blue Carbon-associated sequencing data and metadata to potentially elucidate novel mechanisms behind Blue Carbon dynamics.

Microbiomes of the Sydney Rock Oyster are acquired through both vertical and horizontal transmission.

BACKGROUND: The term holobiont is widely accepted to describe animal hosts and their associated microorganisms. The genomes of all that the holobiont encompasses, are termed the hologenome and it has been proposed as a unit of selection in evolution. To demonstrate that natural selection acts on the hologenome, a significant portion of the associated microbial genomes should be transferred between generations. Using the Sydney Rock Oyster (Saccostrea glomerata) as a model, we tested if the microbes of this broadcast spawning species could be passed down to the next generation by conducting single parent crosses and tracking the microbiome from parent to offspring and throughout early larval stages using 16S rRNA gene amplicon sequencing. From each cross, we sampled adult tissues (mantle, gill, stomach, gonad, eggs or sperm), larvae (D-veliger, umbo, eyed pediveliger, and spat), and the surrounding environment (water and algae feed) for microbial community analysis. RESULTS: We found that each larval stage has a distinct microbiome that is partially influenced by their parental microbiome, particularly the maternal egg microbiome. We also demonstrate the presence of core microbes that are consistent across all families, persist throughout early life stages (from eggs to spat), and are not detected in the microbiomes of the surrounding environment. In addition to the core microbiomes that span all life cycle stages, there is also evidence of environmentally acquired microbial communities, with earlier larval stages (D-veliger and umbo), more influenced by seawater microbiomes, and later larval stages (eyed pediveliger and spat) dominated by microbial members that are specific to oysters and not detected in the surrounding environment. CONCLUSION: Our study characterized the succession of oyster larvae microbiomes from gametes to spat and tracked selected members that persisted across multiple life stages. Overall our findings suggest that both horizontal and vertical transmission routes are possible for the complex microbial communities associated with a broadcast spawning marine invertebrate. We demonstrate that not all members of oyster-associated microbiomes are governed by the same ecological dynamics, which is critical for determining what constitutes a hologenome.

Alternatives to low birthweight as a population-level indicator of infant and child health.

BACKGROUND: Low birthweight (<2500 g) is often used as a population-level indicator of maternal-child health, as it is easy to measure and correlates with poorer infant health outcomes. However, it conflates preterm birth and intrauterine growth restriction, which have different causal pathways and require different approaches to prevention. Small for gestational age (SGA) (a proxy for growth restriction) and preterm birth may be more informative measures. We evaluated low birthweight as a population-level indicator. METHODS: We conducted a population-based cohort study of singleton live births in New South Wales (NSW), Australia, using linked data from 1994-2006 birth, hospital, death and educational records, with follow-up until 2014. Outcomes of babies born of low birthweight, preterm and SGA were compared with well-grown term infants (i.e. not low birthweight or SGA). Overlap between groups and temporal trends were also examined. RESULTS: Of 1 093 765 singleton live births, 47 946 (4.4%) infants were low birthweight and had poorer outcomes than well-grown term infants (2.7% vs. 0.1% infant mortality; 13% vs. 6% below national minimum numeracy standard). SGA and preterm infants also had poorer outcomes (0.5%, 2.3% infant mortality respectively; 10%, 11% below numeracy standard) but 80% of SGA and 47% of preterm infants were not low birthweight. For all outcomes, low birthweight identified a smaller proportion of infants with poor outcomes than preterm birth and than either SGA or low birthweight at term. The proportion of low-birthweight births remained constant over time, while the proportion of births that were preterm increased and proportion of SGA decreased. CONCLUSIONS: Low birthweight, SGA and preterm infants are all at higher risk of poorer outcomes but low birthweight inadequately captures, and masks trends in, both preterm births and births that are SGA. Reporting preterm births and an indicator of growth restriction at term will identify vulnerable groups better than using the measure of low birthweight.

Evaluation of the Respiratory Microbiome and the Use of Tracheal Lavage as a Diagnostic Tool in Kemp's Ridley Sea Turtles (Lepidochelys kempii).

Respiratory disease is a common cause of morbidity and mortality in sea turtles, including the Kemp's ridley sea turtle (Lepidochelys kempii). Although culture-dependent methods are typically used to characterize microbes associated with pneumonia and to determine treatment, culture-independent methods can provide a deeper understanding of the respiratory microbial communities and lead to a more accurate diagnosis. In this study, we characterized the tracheal lavage microbiome from cold-stunned Kemp's ridley sea turtles at three time points during rehabilitation (intake, rehabilitation, and convalescence) by analyzing the 16S rRNA gene collected from tracheal lavage samples. We retrospectively developed a radiographic scoring system to grade the severity of lung abnormalities in these turtles and found no differences in diversity or composition of microbial communities based on radiographic score. We also found that the culture isolates from tracheal lavage samples, as well as other previously reported sea turtle pathogens, were present in variable abundance across sequenced samples. In addition to the tracheal microbial community of live turtles, we characterized microbial communities from other segments of the respiratory tract (glottis, trachea, anterior lung, posterior lung) from deceased turtles. We found a high degree of variability within turtles and a high degree of dissimilarity between different segments of the respiratory tract and the tracheal lavage collected from the same turtle. In summary, we found that the pulmonary microbial community associated with pneumonia in sea turtles is complex and does not correlate well with the microbial community as identified by tracheal lavage. These results underscore the limitations of using tracheal lavage for identification of the causative agents of pneumonia in sea turtles.

Long-Term Fertilization Alters Nitrous Oxide Cycling Dynamics in Salt Marsh Sediments.

Salt marsh sediments are known hotspots for nitrogen cycling, including the production and consumption of nitrous oxide (N2O), a potent greenhouse gas and ozone-depleting agent. Coastal eutrophication, particularly elevated nitrogen loading from the application of fertilizers, is accelerating nitrogen cycling processes in salt marsh sediments. Here, we examine the impact of long-term fertilization on nitrogen cycling processes with a focus on N2O dynamics in a New England salt marsh. By combining 15N-tracer experiments with numerical modeling, we found that both nitrification and denitrification contribute to net N2O production in fertilized sediments. Long-term fertilization increased the relative importance of nitrification to N2O production, likely a result of increased oxygen penetration from nutrient-induced increases in marsh elevation. Substrate utilization rates of key nitrogen cycling processes revealed links between functions and the corresponding microbial communities. Higher specific substrate utilization rates leading to N2O production from nitrification in fertilized sediments indicate a shift in the community composition of ammonia oxidizers, whereas the lack of change in specific substrate utilization of N2O production from denitrification under long-term fertilization suggests resilience of the denitrifying communities. Both are consistent with previous studies on the functional gene community composition in these experimental plots.

Dealing with Anxious Patients: An Integrative Review of the Literature on Nonpharmaceutical Interventions to Reduce Anxiety in Patients Undergoing Medical or Dental Procedures.

Objectives: A previous systematic literature review (SLR) evaluated 501 experiments on reducing patient anxiety across medical and dental environments. This integrative review examines those interventions and explores possible mechanisms leading to relative success or failure within those environments, in the interest of interprofessional education and communication. Methods: Reviewers evaluated 501 experiments testing interventions for reducing patient anxiety in a variety of medical and dental health care settings. Methodology for the SLR, largely following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, is briefly reviewed. Results: A total of 501 experiments (from 408 articles) met review criteria. One hundred and forty-three Music experiments were included, and Music interventions were largely effective, except in the case of colonoscopy. Education is the only intervention that occasionally (5 times of 130 experiments) raised patient anxiety in the face of a procedure; the discussion focuses on the wisdom of assessing patient need for information. Thirty-seven Cognitive Behavioral Therapy (CBT) experiments of various types are included, with a success rate of 89%, with a particularly high rate of success (12 of 12 experiments) in dentistry. Massage has a success rate that is similar to that of CBT, but Massage has been tested in far fewer specialty areas. Relaxation has been tested in every specialty area, except mechanical ventilation, with promising results. Acupuncture and Acupressure have not been widely tested, but their effectiveness rate is 100% when it comes to reducing patient anxiety in various procedural settings. Similarly, experiments show Hypnosis to be successful in 90% of trials. In contrast, Distraction was successful in only 40% of the experiments summarized, although it was more effective in dentistry. A variety of Nature-based Interventions (Aromatherapy, Nature Sounds, and Visual Stimuli) were highly successful across a variety of settings. Discussion: Possible mechanisms are discussed, along with commentary on feasibility. Limitations include publication bias, small sample sizes, and the lack of placebo controls. Future areas of research are pointed out.

Dealing with Anxious Patients: A Systematic Review of the Literature on Nonpharmaceutical Interventions to Reduce Anxiety in Patients Undergoing Medical or Dental Procedures.

Objectives: State (situational) anxiety can create suboptimal outcomes for patients across a variety of health care specializations. While anxiolytic medications reduce anxiety, problematic side effects can compromise outcomes. These challenges have spurred searches for nonpharmaceutical approaches to alleviate patient anxiety. This systematic literature review, largely following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, aimed to determine patterns and effectiveness of interventions across medical health care specialty areas, including dentistry. Methods: A systematic review was conducted, using PubMed, CINAHL, and PsycINFO databases, with search terms related to anxiety, specific interventions, and medical or dental procedures. Hand searching for additional citations was performed on the bibliographies of dissertations, meta-analyses, and systematic reviews that met article inclusion criteria. The search process yielded 48,324 articles and 257 dissertations published in English between 1974 and 2018. Each abstract was evaluated for inclusion by two reviewers, yielding 718 articles that were read and evaluated for outcomes, risk of bias, pretest and post-test, controls and quality, using a Critical Appraisal Skills Programme instrument. Of these, 408 articles, describing 501 experimental trials, were accepted for inclusion in this analysis. Results: A total of 50,343 patients were included in these experiments, with an overall success rate of 71% for reducing patient anxiety. Results are summarized by health care specialty area: surgery, oncology, cardiology, obstetrics/gynecology, dentistry, and pain/trauma, and the following diagnostic testing and intervention areas: imaging, colonoscopy, mechanical ventilation, and other. The largest number of experiments (114) was in the surgery category. The types of interventions included music, education, relaxation, cognitive behavioral therapy (CBT), massage, distraction, hypnosis, acupuncture/acupressure, social support, aromatherapy, nature sounds, natural visual stimuli, special garment, and other. The largest numbers of experiments were done with music (143) and education (130). Discussion: The following interventions were most successful, reducing anxiety in over 70% of experiments: music, CBT, relaxation, massage, acupuncture/acupressure, hypnosis, and natural sounds. Confidence in results is limited by publication bias, small sample sizes, and the lack of placebo controls. Directions for future research are discussed.

Characterization of oral and cloacal microbial communities in cold-stunned Kemp's ridley sea turtles (Lepidochelys kempii) during the time course of rehabilitation.

Microbial communities of animals play a role in health and disease, including immunocompromised conditions. In the northeastern United States, cold-stunning events often cause endangered Kemp's ridley turtles (Lepidochelys kempii) to become stranded on beaches in autumn. These sea turtles are admitted to rehabilitation facilities when rescued alive and are presumed immunocompromised secondary to hypothermia. To better understand the role that microbes play in the health of cold-stunned sea turtles, we characterized the oral and cloacal microbiome from Kemp's ridley turtles at multiple timepoints during rehabilitation, from admission to pre-release, by using Illumina sequencing to analyze the 16S rRNA gene. Microbial communities were distinct between body sites and among turtles that survived and those that died. We found that clinical parameters such as presence of pneumonia or values for various blood analytes did not correlate with oral or cloacal microbial community composition. We also investigated the effect of antibiotics on the microbiome during rehabilitation and prior to release and found that the type of antibiotic altered the microbial community composition, yet overall taxonomic diversity remained the same. The microbiome of cold-stunned Kemp's ridley turtles gradually changed through the course of rehabilitation with environment, antibiotics, and disease status all playing a role in those changes and ultimately the release status of the turtles.

Determining the Composition of Resident and Transient Members of the Oyster Microbiome.

To better understand how complex microbial communities become assembled on eukaryotic hosts, it is essential to disentangle the balance between stochastic and deterministic processes that drive their assembly. Deterministic processes can create consistent patterns of microbiome membership that result in persistent resident communities, while stochastic processes can result in random fluctuation of microbiome members that are transient with regard to their association to the host. We sampled oyster reefs from six different populations across the east coast of the United States. At each site we collected gill tissues for microbial community analysis and additionally collected and shipped live oysters to Northeastern University where they were held in a common garden experiment. We then examined the microbiome shifts in gill tissues weekly for 6 weeks using 16S rRNA gene amplicon sequencing. We found a strong population-specific signal in the microbial community composition of field-sampled oysters. Surprisingly, the oysters sampled during the common garden experiment maintained compositionally distinct gill-associated microbial communities that reflected their wild population of origin, even after rearing them in a common garden for several weeks. This indicates that oyster gill-associated microbiota are predominantly composed of resident microbes specific to host population, rather than being a reflection of their immediate biotic and abiotic surroundings. However, certain bacterial taxa tended to appear more frequently on individuals from different populations than on individuals from the same population, indicating that there is a small portion of the gill microbiome that is transient and is readily exchanged with the environmental pool of microbes. Regardless, the majority of gill-associated microbes were resident members that were specific to each oyster population, suggesting that there are strong deterministic factors that govern a large portion of the gill microbiome. A small portion of the microbial communities, however, was transient and moved among oyster populations, indicating that stochastic assembly also contributes to the oyster gill microbiome. Our results are relevant to the oyster aquaculture industry and oyster conservation efforts because resident members of the oyster microbiome may represent microbes that are important to oyster health and some of these key members vary depending on oyster population.

Rates of neonatal morbidity by maternal region of birth and gestational age in New South Wales, Australia 2003-2016.

INTRODUCTION: Research suggests that neonatal morbidity differs by maternal region of birth at different gestational ages. This study aimed to determine the overall and gestation-specific risk of neonatal morbidity by maternal region of birth, after adjustment for maternal, infant and birth characteristics, for women giving birth in New South Wales, Australia, from 2003 to 2016. MATERIAL AND METHODS: The study utilized a retrospective cohort study design using linked births, hospital and deaths data. Modified Poisson regression was used to determine risk with 95% confidence intervals (95% CI) of neonatal morbidity by maternal region of birth, overall and at each gestational age, compared with Australian or New Zealand-born women giving birth at 39 weeks. RESULTS: There were 1 074 930 live singleton births ≥32 weeks' gestation that met the study inclusion criteria, and 44 394 of these were classified as morbid, giving a neonatal morbidity rate of 4.13 per 100 live births. The gestational age-specific neonatal morbidity rate declined from 32 weeks' gestation, reaching a minimum at 39 weeks in all maternal regions of birth. The unadjusted neonatal morbidity rate was highest in South Asian-born women at most gestations. Adjusted rates of neonatal morbidity between 32 and 44 weeks were significantly lower for babies born to East (adjusted relative risk [aRR] 0.65, 95% CI 0.62-0.68), South-east (aRR 0.76, 95% CI 0.73-0.79) and West Asian-born (aRR 0.93, 95% CI 0.88-0.98) mothers, and higher for babies of Oceanian-born (aRR 1.11, 95% CI 1.04-1.18) mothers, compared with Australian or New Zealand-born mothers. Babies of African, Oceanian, South Asian and West Asian-born women had a lower adjusted risk of neonatal morbidity than Australian or New Zealand-born women until 37 or 38 weeks' gestation, and thereafter an equal or higher risk in the term and post-term periods. CONCLUSIONS: Maternal region of birth is an independent risk factor for neonatal morbidity in New South Wales.

Not All Nitrogen Is Created Equal: Differential Effects of Nitrate and Ammonium Enrichment in Coastal Wetlands.

Excess reactive nitrogen (N) flows from agricultural, suburban, and urban systems to coasts, where it causes eutrophication. Coastal wetlands take up some of this N, thereby ameliorating the impacts on nearshore waters. Although the consequences of N on coastal wetlands have been extensively studied, the effect of the specific form of N is not often considered. Both oxidized N forms (nitrate, NO3-) and reduced forms (ammonium, NH4+) can relieve nutrient limitation and increase primary production. However, unlike NH4+, NO3- can also be used as an electron acceptor for microbial respiration. We present results demonstrating that, in salt marshes, microbes use NO3- to support organic matter decomposition and primary production is less stimulated than when enriched with reduced N. Understanding how different forms of N mediate the balance between primary production and decomposition is essential for managing coastal wetlands as N enrichment and sea level rise continue to assail our coasts.

Sulphide addition favours respiratory ammonification (DNRA) over complete denitrification and alters the active microbial community in salt marsh sediments.

The balance between nitrate respiration pathways, denitrification and dissimilatory nitrate (NO3 - ) reduction to ammonium (DNRA), determines whether bioavailable nitrogen is removed as N2 gas or recycled as ammonium. Saltwater intrusion and organic matter enrichment may increase sulphate reduction leading to sulphide accumulation. We investigated the effects of sulphide on the partitioning of NO3 - between complete denitrification and DNRA and the microbial communities in salt marsh sediments. Complete denitrification significantly decreased with increasing sulphide, resulting in an increase in the contribution of DNRA to NO3 - respiration. Alternative fates of NO3 - became increasingly important at higher sulphide treatments, which could include N2 O production and/or transport into intracellular vacuoles. Higher 16S transcript diversity was observed in the high sulphide treatment, with clear shifts in composition. Generally, low and no sulphide, coupled with high NO3 - , favoured the activity of Campylobacterales, Oceanospirillales and Altermonadales, all of which include opportunistic denitrifiers. High ∑sulphide conditions promoted the activity of potential sulphide oxidizing nitrate reducers (Desulfobulbaceae, Acidiferrobacteraceae and Xanthomonadales) and sulphate reducers (Desulfomonadaceae, Desulfobacteraceae). Our study highlights the tight coupling between N and S cycling, and the implications of these dynamics on the fate of bioavailable N in coastal environments susceptible to intermittent saltwater inundation and organic matter enrichment.

Gestational age, morbidity and mortality among twin births in New South Wales, Australia 2003-2014: A cohort study.

BACKGROUND: Evidence suggests that the trend toward early planned births observed among singletons may be evident among twin pregnancies. AIMS: To describe trends in gestational age at birth, pregnancy characteristics, neonatal morbidity and mortality among twin pregnancies. MATERIALS AND METHODS: Population-based data linkage study of twin births of ≥30 weeks of gestation without a major congenital anomaly born in 2003-2014 in New South Wales (NSW), Australia. Linked pregnancy and birth, hospital and mortality data were used. Generalised linear regression was used to assess linear trends. Risk difference (RD) and 95% confidence intervals were estimated. RESULTS: Among 28 076 eligible twin births (14 038 pregnancies), 49% of births occurred prior to 37 weeks and 69% of births were planned (pre-labour caesarean or induction of labour). There were increases over time in the proportion of twin births at preterm gestations (30-34 weeks (RD 2.1, 95% CI 0.1, 4.0), 35-36 weeks (RD 7.5, 95% CI 5.4, 9.7)) and in the rates of planned births (pre-labour caesarean (RD 6.4, 95% CI 4.0, 8.8), induction (RD 4.6, 95% CI 2.6, 6.6)). There was no significant change in stillbirth or neonatal death rates, but there was an increase in neonatal morbidity over the study period. Concurrently, there were increases in the prevalence of gestational diabetes; and decreases in pregnancy hypertension, assisted reproductive technology use, small-for-gestational age and birthweight discordance. CONCLUSIONS: Gestational age at birth among twin births is decreasing and birth intervention is increasing. There are increasing rates of neonatal morbidity, but no overall change in perinatal mortality.

Nitrate addition stimulates microbial decomposition of organic matter in salt marsh sediments.

Salt marshes sequester carbon at rates more than an order of magnitude greater than their terrestrial counterparts, helping to mitigate climate change. As nitrogen loading to coastal waters continues, primarily in the form of nitrate, it is unclear what effect it will have on carbon storage capacity of these highly productive systems. This uncertainty is largely driven by the dual role nitrate can play in biological processes, where it can serve as a nutrient-stimulating primary production or a thermodynamically favorable electron acceptor fueling heterotrophic metabolism. Here, we used a controlled flow-through reactor experiment to test the role of nitrate as an electron acceptor, and its effect on organic matter decomposition and the associated microbial community in salt marsh sediments. Organic matter decomposition significantly increased in response to nitrate, even at sediment depths typically considered resistant to decomposition. The use of isotope tracers suggests that this pattern was largely driven by stimulated denitrification. Nitrate addition also significantly altered the microbial community and decreased alpha diversity, selecting for taxa belonging to groups known to reduce nitrate and oxidize more complex forms of organic matter. Fourier Transform-Infrared Spectroscopy further supported these results, suggesting that nitrate facilitated decomposition of complex organic matter compounds into more bioavailable forms. Taken together, these results suggest the existence of organic matter pools that only become accessible with nitrate and would otherwise remain stabilized in the sediment. The existence of such pools could have important implications for carbon storage, since greater decomposition rates as N loading increases may result in less overall burial of organic-rich sediment. Given the extent of nitrogen loading along our coastlines, it is imperative that we better understand the resilience of salt marsh systems to nutrient enrichment, especially if we hope to rely on salt marshes, and other blue carbon systems, for long-term carbon storage.